Data communication systems exchange user data for user devices to provide various data communication services. The user devices may be phones, computers, media players, and the like. Wireless base stations are used to extend the range and mobility of the data communication services to the wireless user devices. The wireless base stations are geographically grouped into tracking areas. The tracking areas are used to manage the user devices by general geographic location.
A popular wireless networking protocol is Long Term Evolution (LTE). In LTE networks, user devices wirelessly attach to LTE base stations referred to as evolved Node Bs. The LTE base stations transmit their tracking area IDs to the user devices that they serve. The LTE tracking area IDs include corresponding Public Land Mobile Network (PLMN) IDs. The base stations signal LTE Mobility Management Entities (MMEs) of the attachment and indicate the PLMN IDs. The MMEs access a Home Subscriber System (HSS) database to determine if the user devices are authorized to use their PLMN attachments. If the HSS database returns a PLMN rejection, then the MME notifies the user device and the attachment is blocked. If the HSS database returns a PLMN acceptance, then the MME directs a Serving Gateway (S-GW) to establish a default data bearer for the user device in the attached PLMN.
At some point, the user device may perform an idle-mode handover from its source base station to a target base station. In idle-mode, the user device has default data bearers but no dedicated data bearers. After the idle-mode handover, the user device will report any change in the tracking area ID to its MME in a tracking area update. In response to this tracking area update, the MME directs a new S-GW to establish a new default data bearer for the user device in the new tracking area.
After the new default data bearer is established, the MME accesses the HSS database to determine if the user device is authorized to use the new tracking area. If the HSS database returns a tracking area acceptance, then the MME transfers a tracking area acceptance to the user device over the target base station. If the HSS database returns a tracking area rejection, then the MME signals the S-GW to remove the new default data bearer and transfers a tracking area rejection to the user device. The use of the new tracking area is blocked.
Wireless data communication networks are currently densifying with wireless relays like pico-cell and femto-cell base stations. The pico-cell and femto-cell base stations may use different tracking areas and/or PLMNs from the macro-cell base stations. Due to the internal nesting of these densified base stations, the number of idle-mode handovers is increasing. Unfortunately, not all user devices are authorized to use all the densified PLMNs. Due to the handovers to unauthorized PLMNs, the S-GWs and P-GWs initiate an increasing number of user data bearers that go unused and are later removed.